util/sasl.lua

   1
   2 local md5 = require "util.hashes".md5;
   3 local log = require "util.logger".init("sasl");
   4 local tostring = tostring;
   5 local st = require "util.stanza";
   6 local generate_uuid = require "util.uuid".generate;
   7 local s_match = string.match;
   8 local gmatch = string.gmatch
   9 local string = string
  10 local math = require "math"
  11 local type = type
  12 local error = error
  13 local print = print
  14
  15 module "sasl"
  16
  17 local function new_plain(realm, password_handler)
  18         local object = { mechanism = "PLAIN", realm = realm, password_handler = password_handler}
  19         function object.feed(self, message)
  20
  21                 if message == "" or message == nil then return "failure", "malformed-request" end
  22                 local response = message
  23                 local authorization = s_match(response, "([^&%z]+)")
  24                 local authentication = s_match(response, "%z([^&%z]+)%z")
  25                 local password = s_match(response, "%z[^&%z]+%z([^&%z]+)")
  26
  27                 if authentication == nil or password == nil then return "failure", "malformed-request" end
  28
  29                 local password_encoding, correct_password = self.password_handler(authentication, self.realm, "PLAIN")
  30
  31                 if correct_password == nil then return "failure", "not-authorized"
  32                 elseif correct_password == false then return "failure", "account-disabled" end
  33
  34                 local claimed_password = ""
  35                 if password_encoding == nil then claimed_password = password
  36                 else claimed_password = password_encoding(password) end
  37
  38                 self.username = authentication
  39                 if claimed_password == correct_password then
  40                         return "success"
  41                 else
  42                         return "failure", "not-authorized"
  43                 end
  44         end
  45         return object
  46 end
  47
  48 local function new_digest_md5(realm, password_handler)
  49         --TODO maybe support for authzid
  50
  51         local function serialize(message)
  52                 local data = ""
  53
  54                 if type(message) ~= "table" then error("serialize needs an argument of type table.") end
  55
  56                 -- testing all possible values
  57                 if message["nonce"] then data = data..[[nonce="]]..message.nonce..[[",]] end
  58                 if message["qop"] then data = data..[[qop="]]..message.qop..[[",]] end
  59                 if message["charset"] then data = data..[[charset=]]..message.charset.."," end
  60                 if message["algorithm"] then data = data..[[algorithm=]]..message.algorithm.."," end
  61                 if message["realm"] then data = data..[[realm="]]..message.realm..[[",]] end
  62                 if message["rspauth"] then data = data..[[rspauth=]]..message.rspauth.."," end
  63                 data = data:gsub(",$", "")
  64                 return data
  65         end
  66
  67         local function parse(data)
  68                 message = {}
  69                 for k, v in gmatch(data, [[([%w%-]+)="?([^",]*)"?,?]]) do
  70                         message[k] = v
  71                 end
  72                 return message
  73         end
  74
  75         local object = { mechanism = "DIGEST-MD5", realm = realm, password_handler = password_handler}
  76
  77         --TODO: something better than math.random would be nice, maybe OpenSSL's random number generator
  78         object.nonce = generate_uuid()
  79         object.step = 0
  80         object.nonce_count = {}
  81
  82         function object.feed(self, message)
  83                 self.step = self.step + 1
  84                 if (self.step == 1) then
  85                         local challenge = serialize({   nonce = object.nonce,
  86                                                                                         qop = "auth",
  87                                                                                         charset = "utf-8",
  88                                                                                         algorithm = "md5-sess",
  89                                                                                         realm = self.realm});
  90                         return "challenge", challenge
  91                 elseif (self.step == 2) then
  92                         local response = parse(message)
  93                         -- check for replay attack
  94                         if response["nc"] then
  95                                 if self.nonce_count[response["nc"]] then return "failure", "not-authorized" end
  96                         end
  97
  98                         -- check for username, it's REQUIRED by RFC 2831
  99                         if not response["username"] then
 100                                 return "failure", "malformed-request"
 101                         end
 102                         self["username"] = response["username"]
 103
 104                         -- check for nonce, ...
 105                         if not response["nonce"] then
 106                                 return "failure", "malformed-request"
 107                         else
 108                                 -- check if it's the right nonce
 109                                 if response["nonce"] ~= tostring(self.nonce) then return "failure", "malformed-request" end
 110                         end
 111
 112                         if not response["cnonce"] then return "failure", "malformed-request", "Missing entry for cnonce in SASL message." end
 113                         if not response["qop"] then response["qop"] = "auth" end
 114
 115                         if response["realm"] == nil then response["realm"] = "" end
 116
 117                         local domain = ""
 118                         local protocol = ""
 119                         if response["digest-uri"] then
 120                                 protocol, domain = response["digest-uri"]:match("(%w+)/(.*)$")
 121                                 if protocol == nil or domain == nil then return "failure", "malformed-request" end
 122                         else
 123                                 return "failure", "malformed-request", "Missing entry for digest-uri in SASL message."
 124                         end
 125
 126                         --TODO maybe realm support
 127                         self.username = response["username"]
 128                         local password_encoding, Y = self.password_handler(response["username"], response["realm"], "DIGEST-MD5")
 129                         if Y == nil then return "failure", "not-authorized"
 130                         elseif Y == false then return "failure", "account-disabled" end
 131
 132                         local A1 = Y..":"..response["nonce"]..":"..response["cnonce"]--:authzid
 133                         local A2 = "AUTHENTICATE:"..protocol.."/"..domain
 134
 135                         local HA1 = md5(A1, true)
 136                         local HA2 = md5(A2, true)
 137
 138                         local KD = HA1..":"..response["nonce"]..":"..response["nc"]..":"..response["cnonce"]..":"..response["qop"]..":"..HA2
 139                         local response_value = md5(KD, true)
 140
 141                         if response_value == response["response"] then
 142                                 -- calculate rspauth
 143                                 A2 = ":"..protocol.."/"..domain
 144
 145                                 HA1 = md5(A1, true)
 146                                 HA2 = md5(A2, true)
 147
 148                                 KD = HA1..":"..response["nonce"]..":"..response["nc"]..":"..response["cnonce"]..":"..response["qop"]..":"..HA2
 149                                 local rspauth = md5(KD, true)
 150                                 self.authenticated = true
 151                                 return "challenge", serialize({rspauth = rspauth})
 152                         else
 153                                 return "failure", "not-authorized", "The response provided by the client doesn't match the one we calculated."
 154                         end
 155                 elseif self.step == 3 then
 156                         if self.authenticated ~= nil then return "success"
 157                         else return "failure", "malformed-request" end
 158                 end
 159         end
 160         return object
 161 end
 162
 163 function new(mechanism, realm, password_handler)
 164         local object
 165         if mechanism == "PLAIN" then object = new_plain(realm, password_handler)
 166         elseif mechanism == "DIGEST-MD5" then object = new_digest_md5(realm, password_handler)
 167         else
 168                 log("debug", "Unsupported SASL mechanism: "..tostring(mechanism));
 169                 return nil
 170         end
 171         return object
 172 end
 173
 174 return _M;